Interference control in a broadband powerline communication system

ABSTRACT

A broadband powerline communication system is disclosed which makes use of knowledge of the spectrum characteristics of a local radio environment in order to improve the performance of the system. A determination is made of the spectrum characteristics of a radio environment in the vicinity of the broadband powerline communication system that is transmitting data on modulated carrier frequencies. Certain ones of the carrier frequencies otherwise used by the broadband powerline communication system may be masked (i.e., not used) by all or part of the broadband powerline system in order to avoid interference based on the determination. The spectrum characteristics may be determined 1) in advance and used to compile a configuration database comprising frequency masking parameters; 2) by monitoring the local radio environment using the transmitter/receiver nodes of the system; or 3) based upon receipt of an indication from a conflicting user that the user is experiencing interference. Various combinations of these spectrum characteristic determination techniques may also be used.

This application is a continuation of prior application Ser. No. 11/201,729, filed Aug. 11, 2005, which is a continuation-in-part of prior application Ser. No. 11/074,221, filed Mar. 7, 2005, which claims priority from Provisional Application No. 60/632,326, filed Dec. 1, 2004, each of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to broadband powerline communication systems, and more particularly to interference control in a broadband powerline communication system.

The use of power lines to transmit data is known. Initially, powerline communication systems were limited to relatively low data rates, typically less than 500 kbs. These low data rates are generally useful for applications such as remote control of various switches connected to the powerline system. More recently, developments have been made in the area of broadband powerline communication systems, also known as powerline telecommunications (PLT) systems or broadband powerline (BPL) systems. These systems are capable of transmitting data at significantly higher data rates than previous systems. For example, BPL systems can transmit data at rates of 4-20 Mbps.

While existing powerline systems are capable of transmitting data at the rates described above, they were not initially designed for data transmission. Instead, they were designed to carry large currents at high voltages so that significant amounts of energy could be distributed at one primary low frequency (e.g., 60 Hertz).

Powerline communication systems generally use one or more carrier frequencies in order to spread the data transmission over a wider range of frequencies. The low data rate powerline communication systems discussed above generally utilized frequencies in the range of 9 kHz to 525 kHz. In this frequency range the risk of emissions is low primarily because the wavelengths used in the signaling are long with respect to the typical cable lengths in the system. However, the high data rates of BPL systems cannot be achieved using carrier frequencies below 525 kHz. Instead, BPL systems typically use carrier frequencies in the range of 1-30 MHz. At these higher frequencies the powerline cables become more effective radiators of electromagnetic waves.

One of the problems with a BPL system is the risk of interference, both outbound and inbound. Outbound interference refers to interference to radio communications services caused by the generation of electromagnetic emissions from the powerlines over which the BPL system operates. Inbound interference refers to the detrimental effects of inbound interference from external electromagnetic radiators. The physical attributes of the powerlines (e.g., high elevation and unshielded wiring) along with the higher carrier signal frequencies needed for high bandwidth data transmission, contribute to this interference problem.

BRIEF SUMMARY OF THE INVENTION

The present invention provides improved techniques for reducing interference in a broadband powerline communication system whereby knowledge of the spectrum characteristics of a local radio environment are used in order to improve the performance of a BPL system. In accordance with the principles of the invention, a determination is made of the spectrum characteristics of a radio environment in the vicinity of a broadband powerline communication system that is transmitting data on modulated carrier frequencies. Since the frequencies used by the broadband powerline communication system are shared with other users, and not used exclusively by the broadband powerline communication system, knowledge of spectrum usage by potentially conflicting users may be used to reduce interference. More particularly, certain ones of the carrier frequencies otherwise used by the broadband powerline communication system may be masked (i.e., not used) by all or part of the broadband powerline system in order to avoid interference. In one embodiment, an interference controller node controls the frequency masking by transmitting control instructions to network elements.

In one embodiment, frequency masks may be initiated based upon receipt of an indication from a conflicting user that the user is experiencing interference. In accordance with this embodiment, the transmitter/receiver nodes of the broadband powerline communication system transmit unique identifiers on at least one of the carrier frequencies used by the particular transmitter/receiver node. The unique identifiers identify the particular transmitter/receiver node transmitting such identifier. Receipt of this identifier by a user indicates that the user is receiving interference generally from the broadband powerline communication system, and more particularly from an identifiable transmitter/receiver node. When the broadband powerline communication system receives a notification that a user has received the identifier, then the system may mask appropriate carrier frequencies transmitted by the identified transmitter/receiver node based on the receipt of the identifier from the conflicting user. In a particular embodiment, the unique identifier may be some code, for example, that uniquely identifies the transmitter/receiver node in a particular BPL system . The identifier may include other information as well. The identifiers may be pre-programmed into each of the transmitter/receiver nodes of the system. Alternatively, the identifiers, along with an instruction to transmit the identifier, may be sent in a control instruction from the interference controller. In various embodiments, each unique identifier may identify one particular transmitter/receiver node, or a group of transmitter/receiver nodes. In addition, the transmitter/receivers may transmit the unique identifiers by including them in a transmitted data stream using the same transmission technique as used for transmitting data. Further, a database storing the unique identifiers and their associated transmitter/receiver nodes is accessible by the conflicting users.

These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art broadband powerline communication system;

FIG. 2 illustrates interference in a broadband powerline communication system and shows powerlines and user premises;

FIG. 3 shows a schematic block diagram of a broadband powerline communication system;

FIG. 4 shows a block diagram of an interference controller; and

FIG. 5 shows an exemplary data structure for a database comprising frequency masking parameters.

DETAILED DESCRIPTION

A typical prior art powerline communication system 100 is shown in FIG. 1. A head end network node 106 is connected to a data network 102 via a fiber optic cable 104. In accordance with a typical network service, the head end 106 is configured to transmit data to end user premises (e.g., premises 108) using powerline cables as the transmission medium. The head end 106 is also configured to convert signals in the optical domain received from fiber 104 to the electrical domain using well known optical to electrical conversion techniques. The head end 106 is connected to a transmitter 110. The transmitter 110 contains a modulator 112 which modulates the data received from head end 106 onto a carrier signal using well known RF modulation techniques. As described above, typical carrier frequencies for a powerline communication system are in the range of 2-30 MHz. The modulated signal is provided to the powerline cable 114 via line 116 and coupler 118. A powerline communication system 100 of the type shown in FIG. 1 may use orthogonal frequency division multiplexing (OFDM) in which the available bandwidth is split up into multiple narrowband channels which do not interfere with each other. Thus, in accordance with OFDM transmission, multiple carrier signals, each having its own frequency band and representing a distinct data channel, are carried over the cable 114.

For purposes of the present description, it is assumed that the powerline cable 114 is a medium voltage (MV) powerline cable typically supplying power at 4-66 kV. Such medium voltage cable is typically an aluminum cable having a 1 cm diameter. Coupler 118 couples the modulated carrier signal supplied by line 116 to the MV line 114. Various types of couplers 118 are known in the art. For example, coupler 118 may be an inductive coupler, a capacitive coupler, or may employ direct metallic contact. One type of coupler which may be used is a coupler as described in co-pending U.S. patent application Ser. No. 10/963,144, filed Oct. 12, 2004, entitled Broadband Coupler Technique for Electrical Connection to Power Lines. The carrier signal is transmitted along the length of MV powerline cable 114 to coupler 120 which couples the signal from the MV powerline cable 114 to a receiver 124 via line 122.

The signal from receiver 124 is provided to the premises 108 via low voltage (LV) powerline 128. The low voltage powerline typically supplies power at 100-240 volts. Thus, one of the functions of the receiver is to translate the data from the MV line to the LV line. The low voltage line 128 is connected to a modem 130 within the premises 108. The modem 130 demodulates the signal received from the MV powerline cable 114 and extracts the data that was transmitted from the head end 106. It is noted that in particular embodiments, it is possible that the receiver 124 further functions to demodulate the data and deliver it to a second transmitter (not shown) that would re-modulate the data and send it to the premises 108.

It is noted that for ease of description only downstream (i.e., from head end to end user) data transmission is shown and described. One skilled in the art would readily recognize that upstream transmission could be accomplished in a similar manner. Thus, in a bidirectional system, transmitter 110 and receiver 124 may each be implemented as a transmitter/receiver.

As described above in the background section, one of the problems with BPL systems as shown in FIG. 1 is the effect of both inbound and outbound interference. FIG. 2 illustrates this problem by showing the powerlines 202 which are part of a BPL system and user premises 204, both of which are making use of the same RF frequency spectrum. Since the frequency spectrum used by a typical BPL system is not used solely by the BPL system, there is the potential for interference as illustrated in FIG. 2. The user premises 204 represents a user that is operating in the vicinity of the BPL system and is using at least a portion of the same frequency spectrum as the BPL system. As used herein, the term conflicting user is used to identify any user or user device that is using at least some frequencies that are also used by the BPL system. If the conflicting user 204 is operating in the vicinity of the BPL system, then there is the potential for two types of interference. Transmissions from conflicting user 204 may be received by the powerlines 202 and thus interfere with communications on the BPL system (referred to as inbound interference) and transmissions on the BPL system may be radiated from the powerlines 202 and received by the conflicting user 204 causing interference to the conflicting user (referred to as outbound interference). As seen from this discussion, the term conflicting user is used to identify a user that either causes (or has the potential to cause) interference to the BPL system, or receives (or has the potential to receive) interference from the BPL system. Further, the use of the term inbound or outbound interference is used with respect to the BPL system and as such, outbound interference from the BPL system would be inbound interference to the conflicting user, and inbound interference to the BPL system would be outbound interference from the conflicting user. As would be readily understood by one skilled in the art, the term inbound or outbound is only relevant if the point of reference is known. Unless otherwise indicated herein, the point of reference used herein is that of the BPL system. As used herein, the phrase—in the vicinity of a BPL system—means within a geographic area where there is potential inbound or outbound interference with respect to the BPL system.

A schematic block diagram of a BPL system is shown in FIG. 3 in order to further describe the spectrum characteristics of a radio environment in the vicinity of a BPL system. The BPL system of FIG. 3 shows a number of BPL transmitter/receiver nodes 302, 304, 306, 308, 310 connected by powerlines 320, 322, 324, 326 as shown. Each of the transmitter/receiver nodes is cable of both transmission and receipt of modulated data on various frequencies as described above in conjunction with FIG. 1. Thus, each of the transmitter/receiver nodes 302, 304, 306, 308, 310 combines the transmitter and receiver functionality into a single node. Thus, in exemplary operation, node 302 will transmit data via powerline 320 to node 304, node 304 will receive the transmitted data and will then transmit the data to node 306 via powerline 322. This functionality continues and the data will propagate along the BPL system. The data transmission between any two transmitter/receiver nodes may use frequencies which are the same as, or different from, the data transmission between any two other nodes. This becomes especially useful in the presence of a conflicting user. For example, consider conflicting user 330 in the vicinity of the BPL system as shown in FIG. 3. If conflicting user 330 is transmitting on frequency channel x, then powerline 322 will receive this transmitted signal which will result in interference in the communication channel between transmitter/receiver node 304 and transmitter/receiver node 306 if these nodes are using frequency channel x for data transmission via powerline 322. However, frequency channel x may continue to be used for data transmission between other transmitter/receiver nodes (e.g., between transmitter/receiver node 306 and transmitter/receiver node 308 via powerline 324) because the interfering signal from conflicting user 330 is not strong enough to cause substantial interference on powerline 324. As illustrated in FIG. 3, the area of interference 332 usually encompasses only a limited area. It is to be noted that the area of interference with respect to any particular conflicting user may be different for inbound interference and outbound interference due to the fact that the power of interfering signals radiated from the BPL system may be different than the power of interfering signals radiated from the conflicting user.

The converse situation is similar, in which the BPL system is transmitting data on frequency channel x between transmitter/receiver nodes 304 and 306 via powerline 322, and is therefore radiating signals into the vicinity of the BPL system on channel x. As such, conflicting user 330 will receive this transmitted signal which will result in interference at the conflicting user 330. However, frequency channel x may continue to be used for data transmission between other transmitter/receiver nodes (e.g., between transmitter/receiver node 306 and transmitter/receiver node 308 via powerline 324) without interfering with conflicting user 330 because the interfering signal radiating from powerlines other than powerline 322 will not be strong enough to cause substantial interference at conflicting user 330. Again, as illustrated in FIG. 3, the area of interference 332 usually encompasses only a limited area.

In view of the above, knowledge of the spectrum characteristics of a local radio environment can be used in order to improve the performance of a BPL system in accordance with the principles of the present invention. In accordance with the principles of the invention, a determination is made as to the spectrum characteristics of a radio environment in the vicinity of a BPL system that is transmitting data on modulated carrier frequencies. Since the frequencies used by the BPL system are shared with other users, and not used exclusively by the BPL system, knowledge of spectrum usage by interfering users may be used to reduce interference. More particularly, certain ones of the carrier frequencies otherwise used by the BPL system may be masked (i.e., not used) by all or part of the BPL system in order to avoid interference.

The spectrum characteristics in the vicinity of the BPL system may be determined in advance and used to compile a database of known conflicting users and the characteristics of their spectrum usage. Various information may be compiled in accordance with this embodiment of the invention. For example, and without limitation, such information about a conflicting user may include: the particular frequency or frequencies used, the days and/or times the frequencies are used, the geographic area in which the conflicting user's transmitted signals may be strong enough to interfere with the BPL system, and the geographic area in which the BPL system's transmitted signals may be strong enough to interfere with the conflicting user. The compilation and analysis of this information will allow for the maintenance of a configuration database which may be used in order to dynamically configure the BPL system. If conflicting uses of the radio spectrum in a particular geographic area are known in advance, then those conflicting uses can be avoided by masking certain radio frequencies in portions of the BPL system. For example, returning to the example of FIG. 3, if it is known that conflicting user 330 is transmitting or receiving on frequency channel x, and area of interference 332 with respect to this conflicting user is also known, then the BPL system may mask out frequency channel x within the area of interference 332.

Additional information about the conflicting use may also be used in order to configure the BPL system. For example, it may be known that the conflicting use of a particular frequency channel by a particular conflicting user only occurs on certain days, certain times, or some combination of days and times. This information may be used in order to mask out certain frequencies only when necessary to avoid the interference, so that the full spectrum may continue to be used at other times.

This information may be compiled in various ways. For example, a survey of the geographic area in the vicinity of the BPL system may be made by technicians using various radio monitoring equipment so that over some period of time the spectrum usage characteristics may be determined. Alternatively, potential conflicting users in the geographic area may supply information as to their usage of the radio spectrum. Another alternative is that the BPL system may detect various types of conflicting use over time and collect this information for later use. Yet another alternative is that some central authority may notify the service provider operating the BPL system about local spectrum usage.

An apparatus which may be used in order to implement an embodiment of the invention is shown in FIG. 4. FIG. 4 shows an interference controller 402. The components of interference controller 402 will be described herein at a high level using a functional description in order to convey an understanding of the function of interference controller 402. Using this description, one skilled in the art could readily implement an interference controller 402 using various hardware, software, and combinations of hardware and software. One such implementation could include a programmable computer of the type which is well known in the art. Returning to FIG. 4, the overall operation of interference controller 402 is controlled by a processor 404 which operates to control the interference controller 402 by executing stored computer program code which defines the desired operation. The stored computer program code is stored in storage/memory 410 which may be implemented using any type of computer readable medium, including magnetic, electrical, optical, or other type of media. Processor 404 is also connected to a database 412 (database 412 is shown separately as a functional entity, but one skilled in the art will recognize that database 412 may be implemented using separate storage and logic components, or it may be integrated into storage/memory 410). Database 412 defines parameters for frequency masking in order to reduce interference in the vicinity of the BPL system. These parameters may be determined based on the above described compiled spectrum usage characteristics.

One particular exemplary data structure for database 412 is shown in FIG. 5. The database 500 shown in FIG. 5 contains various fields which are used in order to control the masking of frequencies in the BPL system. Field 502 contains a time/date range, field 504 contains transmitter/receiver node identifications, and field 506 contains a list of masked frequencies. One exemplary record in database 500 is shown as record 510. The time/date range field 502 of record 510 indicates that the mask is to be effective on Tuesdays and Fridays from 6-8pm. As an example, this type of mask may be used if there is a conflicting user in the form of a HAM radio operator who operates his/her radio station only on Tuesday and Friday evenings. Field 504 of record 510 identifies the particular BPL transmitter/receiver nodes that are affected by this mask. More particularly, field 504 indicates pairs of adjacent transmitter/receiver nodes, such that an identified pair of adjacent transmitter/receiver nodes do not communicate with each other via a masked frequency. In the particular case of record 510, the interference area involves the path between two transmitter/receiver nodes (having identifications 17436 and 17437). Field 506 identifies the particular frequency channels to be masked. In the example of FIG. 5, the masked frequencies are directly specified, but alternatively the masked frequencies may be identified by channel identifiers (e.g., channel A) which have previously been associated with particular frequency ranges. In the example record 510, the frequency range to be masked is the frequency range of 5-7 MHz. Thus, record 510 indicates that on Tuesdays and Thursdays between 6 and 8 PM transmitter/receiver nodes 17436 and 17437 have a mask on the 5-7 MHz frequency range. One skilled in the art will recognize that various combinations of data may be present in the database of FIG. 5 in order to contain information which is functionally equivalent to the information shown in FIG. 5. For example, while the records of database 500 as described contain the days and times that certain frequencies are masked at particular transmitter/receiver nodes, the database could alternatively contain the days and times that certain frequencies are allowed to be used at particular transmitter/receiver nodes. One skilled in the art would recognize that these two uses of database 500 are functionally equivalent, and that other various functionally equivalent alternatives may also be designed. Further, various additional information may be stored in database 500 in various implementations. For example, the name of a HAM (or other) operator as well as relevant FCC licensing information may be stored.

Returning now to FIG. 4, the interference controller 402 uses the information in database 412 in order to determine the necessary frequency masking for a

BPL system. The interference controller 402 utilizes clock 406 in conjunction with database 412 in order to determine when particular frequency masks need to take affect. Interference controller 402 also contains a network interface 414 which is used to communicate instructions to the various transmitter/receiver nodes in the BPL system. The interface controller 402 may be directly connected to the BPL system via a powerline, or alternatively the interference controller 402 may be connected to the various transmitter/receiver nodes via some other network connection (e.g., LAN, WAN, Internet, wireless). Regardless of the particular network connection, the interference controller 402, using its clock 406, internal logic and the contents of database 412, determines when particular frequency masks need to be implemented at particular transmitter/receiver nodes, and sends appropriate control instructions to these particular transmitter/receiver nodes via network interface 414. The transmitter/receiver nodes are configured such that upon receipt of a control instruction from interference controller 402 indicating that a particular frequency should be masked, the transmitter/receiver will stop transmitting and receiving on that frequency.

As shown in FIG. 4, interference controller 402 also contains an I/O module 408 which represents user interface elements (e.g., keyboard, mouse, display screen, etc.) to allow user interaction with the interference controller 402. This allows a user to manually modify the contents of database 412, or to manually send control instructions to the transmitter/receiver modules.

The spectrum characteristics in the vicinity of the BPL system may be monitored in order to determine appropriate frequency masks for the system. In accordance with this technique, the transmitter/receiver nodes monitor the various received frequencies to determine if there is interference (e.g., an incoming signal above some threshold) present on any of the frequency channels. The monitoring may be done by the BPL system turning off all transmissions periodically (i.e., a quiet time) and listening for any received signals during this quiet time. If a signal is received during the quiet time, then it means that it was received from a conflicting user, which is an indication of incoming interference on a particular frequency, and also an indication of possible outgoing interference if the BPL system uses the same frequency. The information about the local radio environment as determined by the individual transmitter/receiver nodes is then transmitted to the interference controller 402 via its network interface 414. As described above, the interference controller 402 may be directly connected to the BPL system via a powerline, or alternatively the interference controller 402 may be connected to the various transmitter/receiver nodes via some other network connection (e.g., LAN, WAN, Internet, wireless).

Upon receipt of the information from the various transmitter/receiver nodes, the interference controller 402 determines which frequency channels to mask for particular transmitter/receiver nodes. The interference controller 402 may determine to mask out interfering frequencies within a particular interference area for a particular time period. After the time period, the controller 402 may institute another quiet period to listen for interference, and adjust the frequency masks as necessary to adapt to the new local radio environment. The control of the above described monitoring activity may be controlled and coordinated via the interference controller 402, whereby the interference controller 402 sends appropriate control instructions to the transmitter/receiver nodes to control the monitoring and associated masking. For example, the initiation of the quit period and the monitoring for interference can be performed by the transmitter/receiver nodes in response to receipt of a control instruction from interference controller 402. Alternatively, the transmitter/receiver nodes could be configured to perform the monitoring on some predetermined schedule. One skilled in the art would recognize that there are various alternatives possible for this monitoring. For example, all frequency channels could be monitored for interference during each quiet period, or alternatively, some subset of the frequency channels could be monitored.

The monitoring of the local radio environment as described above is particularly advantageous to detect and compensate for unpredictable interference situations (e.g., emergency use of various frequency bands).

In accordance with an embodiment of the invention, frequency masks may be initiated based upon receipt of an indication from a conflicting user that the user is experiencing interference. This is an indication that the conflicting user has received an identifier associated with one or more transmitter/receiver nodes of the BPL system. In accordance with this embodiment, each of the transmitter/receiver nodes of the BPL system periodically transmits a unique identifier on one or more frequencies. In an advantageous embodiment, the unique identifiers are transmitted on each of the carrier frequencies used by the BPL system, thus ensuring that a user experiencing interference from the BPL system will be able to receive the identifier even if the user is only capable of receiving a limited number of frequencies. The unique identifier may be some code, for example, that uniquely identifies the transmitting transmitter/receiver node , or that identifies the service provider operating the BPL system. Alternatively, rather than the unique identifier identifying one transmitter/receiver node, the identifier may identify some group of transmitter/receiver nodes. The identifier may include other information as well. The appropriate identifier and transmission period may be pre-programmed into each of the transmitter/receiver nodes of the system. Alternatively, the appropriate identifier, along with an instruction to transmit the identifier, may be sent in a control instruction from the interference controller 402. The unique identifier may be transmitted by the transmitter/receiver nodes by including the identifiers in a transmitted data stream using the same transmission technique as used for the transmission of data. Thus, no special signaling technique is required on the part of the transmitter/receiver nodes in order to transmit the unique identifiers. In a particular embodiment, the unique identifier is scheduled on various frequencies at different times to avoid suspension of all data transmission during transmission of the identifier.

Upon receipt of interference (including the unique identifier) on a particular frequency channel, a conflicting user may identify the source of interference by associating the received unique identifier with the BPL system and/or the service provider operating the system. Alternatively, the received unique identifier may be provided to a third party (e.g., local government authority) to determine the source of interference.

In one embodiment of the invention, the BPL service provider (or other entity) maintains a database that associates the unique identifiers with the BPL system and/or particular transmitter/receiver nodes (or groups of nodes) of the BPL system. This database may be accessible by the conflicting user receiving the unique identifier so that the conflicting user may determine the BPL system causing the interference and/or the particular transmitter/receiver node (or group of nodes) of the BPL system that is causing the interference. In alternate embodiments, the BPL service provider may make some of the database information accessible to the public, while other information is not. For example, the BPL service provider may allow conflicting users to access the database with a received identifier and determine the identify of the BPL service provider, but not allow conflicting users to access the data associating unique identifiers with particular transmitter/receiver nodes. In yet other embodiments, the database information may not be accessible the by the public, but instead is accessible by certain government entities, or emergency services personnel. Of course, various alternatives exist with respect to database access rights, and such various alternatives would be readily apparent to one of ordinary skill in the art given the description herein.

When the service provider operating the BPL system receives an indication that a unique identifier has been received, certain appropriate masking of frequency channels may be initiated. For example, a user may use input/output module 408 of interference controller 402 to implement appropriate masking to eliminate the interference. Alternatively, a user may use input/output module 408 to add an appropriate record to database 412 as described above so that appropriate masking will be automatically handled by the interference controller 402 at appropriate times. In accordance with one advantage of the invention, the particular transmitter/receiver nodes that are causing the interference may be identified by the unique identifiers, and as such the appropriate masking may be tailored to the specific BPL nodes that are causing the interference. This allows for a more efficient masking process.

The transmission of unique identifiers is advantageous to control outbound interference with respect to conflicting users who are receiving RF signals, but who are not transmitting signals. The lack of transmission would mean that the BPL system would not detect any conflicting use by using the monitoring techniques described above. As such, the transmission of an identifier allows the BPL system to mask frequency channels that are interfering with users who are receiving RF signals, but not transmitting. One advantageous use of this embodiment is in an emergency situation, in which local authorities using a particular radio frequency are experiencing interference. These authorities could recognize the unique identifier and therefore identify the source of the interference (e.g., the particular transmitter/receiver node). The authorities could then contact the service provider operating the BPL system in order to have the service provider mask out the interfering radio frequencies on the appropriate one or more transmitter/receiver nodes. Alternatively, the local authorities could have direct access to the interference controller 402 (e.g., via network interface 414) and could immediately mask out the interfering radio frequencies themselves. In severe emergency situations, the local authorities could even shut down all RF transmissions on the BPL system via access to the interference controller 402.

With reference again to FIG. 3, it is to be noted that although interference area 332 will be a limited geographic area, it is possible that that such area might not be in the immediate vicinity of the BPL system. In an extreme case, interference from the BPL system might “bounce” off the high-altitude ionospheric layer of the atmosphere and return to earth one thousand or more miles away. In such a situation, the present invention provides the additional advantage of identifying the interfering BPL system, or nodes within the BPL system, where such identification would not otherwise be apparent due to the distance between the BPL system and the conflicting user. In such cases, the conflicting user may otherwise mis-identify a local BPL system as the source of the interference. However, a system in accordance with the present invention solves this mis-identification problem.

The foregoing Detailed Description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention. For example, in addition to the masking of certain frequency channels as described above, it is also possible to initiate data transmission on alternate frequency channels upon a determination that certain frequency channels need to be masked. Further, one skilled in the art would recognize that various combinations of embodiments are also possible in accordance with the principles of the present invention. 

The invention claimed is:
 1. A method for controlling interference in a broadband powerline communication system that is transmitting data on modulated carrier frequencies not used exclusively by the broadband powerline communication system, the method comprising: compiling a database of a plurality of characteristics of usage of a spectrum by a plurality of conflicting users in a vicinity of the broadband powerline communication system, wherein the plurality of characteristics of usage of the spectrum by the conflicting users in the vicinity of the broadband powerline communication system comprises: a list of particular time intervals during which the spectrum is used by each of the plurality of conflicting users; a list of carrier frequencies used by each of the plurality of conflicting users; a geographical area in which each of the plurality of conflicting users interferes with the broadband powerline communication system; and a combination of a particular time interval and a particular carrier frequency used by each of conflicting users in the vicinity of the broadband powerline communication system; generating a schedule of use of the spectrum by each of the plurality of conflicting users based on each of the plurality of characteristics of usage; and masking a carrier frequency at one of the transceiver nodes based on the schedule.
 2. The method of claim 1, wherein the conflicting users are users that use a same carrier frequency as a carrier frequency used by transceiver nodes of the broadband powerline communication system during a same period of time.
 3. The method of claim 1, wherein compiling a database comprises: transmitting a unique identifier from a transceiver node in the broadband powerline communication system on a particular carrier frequency, the unique identifier identifying the transceiver node; receiving an indication from a conflicting user that the unique identifier has been received by the conflicting user, the indication received at a particular time.
 4. The method of claim 3, wherein transmitting the unique identifier comprises transmitting the unique identifier using a transmission technique that is used for transmitting the data.
 5. The method of claim 3, wherein the unique identifier identifies a single transceiver node in the broadband powerline communication system.
 6. The method of claim 3, wherein the unique identifier identifies a plurality of transceiver nodes in the broadband powerline communication system.
 7. An apparatus comprising: a processor; and a memory to store computer program instructions, the computer program instructions for controlling interference in a broadband powerline communication system that is transmitting data on modulated carrier frequencies not used exclusively by the broadband powerline communication system, when executed on a processor, cause the processor to perform operations comprising: compiling a database of a plurality of characteristics of usage of a spectrum by a plurality of conflicting users in a vicinity of the broadband powerline communication system, wherein the plurality of characteristics of usage of the spectrum by the conflicting users in the vicinity of the broadband powerline communication system comprises: a list of particular time intervals during which the spectrum is used by each of the plurality of conflicting users; a list of carrier frequencies used by each of the plurality of conflicting users; a geographical area in which each of the plurality of conflicting users interferes with the broadband powerline communication system; and a combination of a particular time interval and a particular carrier frequency used by each of conflicting users in the vicinity of the broadband powerline communication system; generating a schedule of use of the spectrum by each of the plurality of conflicting users based on each of the plurality of characteristics of usage; and masking a carrier frequency at one of the transceiver nodes based on the schedule.
 8. The apparatus of claim 7, wherein the conflicting users are users that use a same carrier frequency as a carrier frequency used by transceiver nodes of the broadband powerline communication system during a same period of time.
 9. The apparatus of claim 7, wherein compiling a database comprises: transmitting a unique identifier from a transceiver node in the broadband powerline communication system on a particular carrier frequency, the unique identifier identifying the transceiver node; receiving an indication from a conflicting user that the unique identifier has been received by the conflicting user, the indication received at a particular time.
 10. The apparatus of claim 9, wherein transmitting the unique identifier comprises transmitting the unique identifier using a transmission technique that is used for transmitting the data.
 11. The apparatus of claim 9, wherein the unique identifier identifies a single transceiver node in the broadband powerline communication system.
 12. The apparatus of claim 9, wherein the unique identifier identifies a plurality of transceiver nodes in the broadband powerline communication system.
 13. A non-transitory computer-readable medium storing computer program instructions for controlling interference in a broadband powerline communication system that is transmitting data on modulated carrier frequencies not used exclusively by the broadband powerline communication system, which, when executed on a processor, cause the processor to perform operations comprising: compiling a database of a plurality of characteristics of usage of a spectrum by a plurality of conflicting users in a vicinity of the broadband powerline communication system, wherein the plurality of characteristics of usage of the spectrum by the conflicting users in the vicinity of the broadband powerline communication system comprises: a list of particular time intervals during which the spectrum is used by each of the plurality of conflicting users; a list of carrier frequencies used by each of the plurality of conflicting users; a geographical area in which each of the plurality of conflicting users interferes with the broadband powerline communication system; and a combination of a particular time interval and a particular carrier frequency used by each of conflicting users in the vicinity of the broadband powerline communication system; generating a schedule of use of the spectrum by each of the plurality of conflicting users based on each of the plurality of characteristics of usage; and masking a carrier frequency at one of the transceiver nodes based on the schedule.
 14. The non-transitory computer-readable medium of claim 13, wherein the conflicting users are users that use a same carrier frequency as a carrier frequency used by transceiver nodes of the broadband powerline communication system during a same period of time.
 15. The non-transitory computer-readable medium of claim 13, wherein compiling a database comprises: transmitting a unique identifier from a transceiver node in the broadband powerline communication system on a particular carrier frequency, the unique identifier identifying the transceiver node; receiving an indication from a conflicting user that the unique identifier has been received by the conflicting user, the indication received at a particular time.
 16. The non-transitory computer-readable medium of claim 15, wherein transmitting the unique identifier comprises transmitting the unique identifier using a transmission technique that is used for transmitting the data.
 17. The non-transitory computer-readable medium of claim 15, wherein the unique identifier identifies a single transceiver node in the broadband powerline communication system.
 18. The non-transitory computer-readable medium of claim 15, wherein the unique identifier identifies a plurality of transceiver nodes in the broadband powerline communication system. 